Fertilizing tomatoes correctly depends on several factors:
Under suitable conditions, high-yielding tomato varieties are expected to produce 100-150 tonnes per hectare. Determinate tomato varieties need fertilization to support sustained growth and at the same time the ripening of fruit with high market value.
The nitrogen supply must be sufficient for as long as growth continues. However, an excess supply of nitrogen can affect fruit quality and delay ripening. At this stage, ammonium (NH4+) is the preferred nitrogen form. Appropriate phosphorus and potassium levels ensure high quality (taste, colour, firmness and shelf-life). Ensuring the necessary potassium level is important for fruit formation and fruit enlargement. Calcium deficiency induces blight, often as a result of unfavourable summer climates. The optimum pH value of the soil is between 6.5 and 7. Tomatoes are not only sensitive to salt, but also to zinc, iron, boron and manganese deficiencies. Sulphur fertilizer in particular improves the firmness and colour of the fruit. Dose splitting is necessary. The amount of calcium necessary for the tomatoes is applied prior to planting in autumn.
Fertigation facilitates the adaption of fertilizer composition and quantity to different growth phases.
Yield parameters of tomatoes:
- Number of plants/m²
- Number of fruits/plant
- Fruit weight
The amount of shoots per m² and a continuous production of flowers and fruit determine the yield. For this, especially at the beginning, nitrogen and magnesium supply is important. For well-developed tomatoes with a healthy and strong colour and classic taste, it is important to have sufficient potassium, no oversupply of calcium, and sufficient sulphur and water.